Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$208.49	10.188%	$229.731	$229.73	$229.75	$229.70
Purchase #2	$155.55	4.429%	$162.4393	$162.44	$162.45	$162.40
Purchase #3	$26.86	5.862%	$28.4345	$28.43	$28.45	$28.40
Purchase #4	$144.34	9.606%	$158.2053	$158.21	$158.20	$158.20
Purchase #5	$184.96	13.785%	$210.4567	$210.46	$210.45	$210.50
Purchase #6	$119.87	3.203%	$123.7094	$123.71	$123.70	$123.70
Purchase #7	$80.92	10.771%	$89.6359	$89.64	$89.65	$89.60
7 purchase totals =	$920.99		$1,002.6121	$1,002.62	$1,002.65	$1,002.50